This invention relates to what is generally known as the completion of subterranean wells. Generally, such wells are created for producing hydrocarbons from a subterranean formation. As part of the overall process of producing hydrocarbons, in some cases, a subterranean formation can be treated or injected with fluids or slurries, including but not limited to water, steam, gas, acids, and sand slurries. More particularly, embodiments of the invention relate to a completion system for conveying tools that can aid with performing such treatments, and more generally that can aid with performing, production, stimulation, intervention, injection, or other operations related to the production of hydrocarbons at specific locations within a subterranean well. “Completion” is a generic term used to generally describe any action or treatment in a well, field, or reservoir to stimulate, enhance, improve, increase or decrease one or more of the following; flow or production performance, longevity of the flow or production performance, the total recoverable hydrocarbons, percentage of water produced; or percentage of gas produced. “Completion System” is a generic term used to generally describe any component or combination of components that perform any completion in one (1) or more zones, by diverting flow, splitting flow, directing flow, isolating one zone or interval from another zone or interval; and, stopping, starting, controlling or regulating flow in or out of any zone, production, stimulation, or injection operations. Tools may include, but are not limited to one or more of the following, plugs, darts, down hole pressure/temperature gauges, flow regulators, sliding sleeves, safety valves, check valves, perforating guns, shifting tools and packers for subdividing the well into different production zones. Operations may also include but are not limited to one or more of the following; positioning a down hole gauge, perforating or otherwise making one or more holes in a well tubular, opening otherwise repositioning a down hole sliding sleeve, installing, activating or otherwise manipulating an artificial lift device, and installing, a permanent or temporary plugging device which may contain a core that is in whole or in part meltable, degradable, disintegrable, removable or otherwise disappearing.
In a staged or zoned wellbore completion operation, a well is divided into multiple zones, also referred to as “stages” or “intervals.” Each zone can be fluid-isolated and/or pressure isolated from other zones, in whole or in part, so it can be treated independently of other zones to resolve various conditions in that zone. Those skilled in the art will appreciate that in many situations where one is attempting to pressure-isolate or fluid-isolate one zone from another, though substantial isolation may be achieved, seepage of pressure or fluids across zones may nonetheless occur. Therefore, isolation, fluid-isolation, and pressure-isolation encompasses such situations, whether or not such seepage occurs.
In many subterranean wells, desirable to have portions of the well sub-divided in smaller zones, which means having a higher number of zones for a well of a given length. With reference to FIG. 1, an example of a wellbore completion system is shown, which can be used to effect treatment of a formation 10 through a wellbore 12. Treatment of a formation may include e.g., deploying stimulation fluids into, the formation, injecting fluids sometimes above the fracture gradient away from the wellbore into the formation, and moving hydrocarbons from the formation to surface.
The wellbore completion system referenced in FIG. 1 includes a tubing string 14, sometimes referenced as a liner, having an uphole end 14b extending toward surface and a downhole end 14a. The tubing string 14 comprises a plurality of spaced apart port subs 16a to 16e that each include one or more ports 17a to 17e opened through the tubing string wall to permit access between the tubing string inner bore 18 and the wellbore 12. A packer or other isolation device 20a is mounted between the upper-most port sub 16a and the surface, and further packers 20b to 20f mounted between each pair of adjacent port subs. In some systems, there can be more than one packer between the port subs. The packers are each disposed about the tubing string 14, encircling it and positioned to seal the annulus between the tubing string 14 and the wellbore wall. Thus, fluid and/or pressure is significantly or completely prevented from passing through the annulus into adjacent zones, and the packers 20 thus divide the wellbore 12 into zones that are isolated from each other and that can be individually treated, produced or injected. A treatment can be applied to one or more zones in the well at any one time. Typically, one sub is deployed in each zone, but more than one can be deployed in a zone.
To treat a zone, an operator is able to operate a tool in a particular zone at a given point in time, while isolating that zone from other zones. This operation can be achieved by conveying a tool to a targeted sub within that zone. It can also involve, in the case of a tool that has already been preinstalled into a sub 16a-16e at a targeted zone, the timely conveyance of balls, darts or plugs that trigger, engage or support the operation of the preinstalled tool at the sub covering that zone.